A product where an absorbent part formed of crushed pulp and the like is provided between a top sheet and a back sheet, is conventionally used as an absorbent product such as a disposable diaper or an auxiliary absorbent pad. In Published Japanese Translation No. 9-504206 of PCT International Application No. PCT/US94/11707 (Document 1), Published Japanese Translation No. 9-504207 of PCT International Application No. PCT/US94/11708 (Document 2), Published Japanese Translation No. 9-504208 of PCT International Application No. PCT/US94/11709 (Document 3) and Published Japanese Translation No. 9-504210 of PCT International Application No. PCT/US94/11752 (Document 4), laminated structure of a fiber assembly layer of pulp or the like and an absorbent sheet where super absorbent materials are located in a plurality of pocket regions provided between two carrier layers, is proposed as an absorbent part of a disposable diaper.
Japanese Patent Application Laid-Open No. 8-191857 (Document 5) discloses an absorbent part where an upper core having an opening is laminated on a lower core through a hydrophilic nonwoven fabric. In a disposable diaper of Document 5, moisture of excrement toward an upper surface of the upper core is absorbed thereat, moisture which has passed through the opening of the upper core is received by the hydrophilic nonwoven fabric to be diffused, and therefore it is absorbed at boundary surfaces between the upper core and the lower core. In Japanese Patent Application Laid-Open No. 2005-185616 (Document 6), a disposable absorbent product where a diffusion layer is provided at a space within an opening of an upper core is proposed.
In a super absorbent material such as SAP (Super Absorbent Polymer) used for a disposable diaper or the like, moisture is slowly absorbed as compared to a fiber assembly layer of pulp or the like. Thus, in the case where an absorbent sheet having super absorbent materials is located on the fiber assembly layer of pulp or the like as shown in the disposable diapers of Documents 1 to 4, before moisture of excrement is absorbed into the absorbent sheet, the moisture possibly spreads widely to reach to the skin of the wearer or to leak out to the outer side of the disposable diaper.
In the disposable diapers of Documents 5 and 6, since the lower core is the fiber assembly layer of pulp or the like having relatively high absorption speed, moisture of excrement which has passed through the opening of the upper core is absorbed into the lower core before it is diffused widely by the hydrophilic nonwoven fabric. Thus, the moisture of excrement is mainly absorbed into portions of the upper and lower cores positioned in the vicinity of the opening, and whole the upper and lower cores can not be utilized efficiently to absorb moisture. Consequently, if after excretion, excretion is performed again without changing the disposable diaper, some moisture of excrement is not possibly absorbed and flows back through the opening, to reach over a wide area of the skin of the wearer or to leak out to the outer side of the disposable diaper. In addition, by the first excretion, the portions of the upper and lower cores positioned in the vicinity of the opening are swollen by absorption of moisture and the portions come into contact with each other with no space between them, and therefore the moisture of excrement which has passed through the opening is more poorly diffused in the second excretion and later.